The TCNA Handbook for Ceramic, Glass, and Stone Tile Installation highlights the building designer’s responsibility to know how each tile installation will be used and maintained, to avoid under-designing an area for the amount of water it will be exposed to. Courtesy of the Tile Council of North America, Inc. (TCNA).
I talk to many people who are not clear on when and where to use waterproofing under tile installations. The most surprising thing I come across is those who think that tile, grout, mortar and backer board are waterproof. Unfortunately, there are many failed installations due to the lack of waterproofing and improper waterproofing, so let’s look at when to consider using waterproofing under tile.
A good place to start is the Tile Council of North America (TCNA) Handbook, which addresses waterproofing in several places. There are specific sections such as the “Membrane Selection Guide” and the “Wet Area Guidelines” that discuss membrane usage. The Membrane Selection Guide outlines several different types of waterproofing, from non-metallic, lead, copper, CPE and PVC. There are also the ANSI A118.10 trowel-applied sheet or liquid waterproof membranes commonly familiar to the tile trades. Sometimes these are referred to as fluid-applied membranes. Once cured, these ANSI A118.10 membranes are designed to provide a continuous membrane that tile can be directly bonded to.
The Wet Area Guidelines section in the TCNA Handbook is a very useful for understanding the requirements for waterproof membranes. In addition to discussing the environmental exposure classification, this section also discusses proper slope required for wet areas, as well as the different types of drains, such as clamping drains and integrated bonding flange drains. One of the most important topics discussed in this section is performing the water test, commonly called a flood test or 24-hour test. Testing the ability for the area to properly hold water is an important factor to know prior to installing tile and is required by certain municipalities.
Many TCNA Handbook methods include the possible use of a membrane, leaving the design professional to determine whether one is needed, based on the expected water exposure.
Within the TCNA Handbook methods, such as F141-19, the diagram shows the option for a membrane and below the diagram it states, “*Use of a membrane is optional. See membrane options.” Does that mean a membrane usage is optional at the discretion of the installer? No, first, it’s important to understand the designed usage of the space and its Environmental Exposure Classification. The Environmental Exposure Classification section in the TCNA Handbook is often overlooked and yet it holds a wealth of information with regards to the intended usage of a space and thus the proper classification. These classifications are divided into two categories, residential (res) and commercial (com). Both the residential and commercial categories are further divided into seven separate classifications, each with its own expected water exposure.
In the example TCNA F141-19, the area is designed with limited water exposure has a rating of Res1,2/Com1,2. If this space is going to be used as a commercial kitchen for instance, this area is typically designed with limited
Commercial kitchen maintenance practices vary widely. Some are routinely saturated during cleaning and require a membrane.
water exposure in mind, giving it a Com2 usage rating. The difference could be as simple as how the space is cleaned, do they intend to hose down the walls and floor? If so, the area would need to be designed for increased water exposure as outlined in the membrane options within the TCNA F141-19. Typically, in this type of situation, the flashing connections to the walls and any drains need to be addressed to create a complete waterproof system.
As you can see, there are a lot of considerations for the proper selection and use of waterproof membranes. If you have specific questions, contact a membrane manufacturer and they can help with the correct choice of material. Some manufacturers even provide job site support for the proper installation of their material. I’ll leave you with my simple rule of thumb, if it’s going to see water exposure, waterproof it – because in the end it’s cheaper than a failure.
There are many factors to consider before selecting an appropriate grout joint width for porcelain and ceramic tiles. Factors that affect proper specification, by way of example but without limitation, include the tile’s dimensional tolerances such as allowable warping and out of square per ANSI A137.1 manufacturing standards, floor flatness, size of the area being tiled, and the presence of movement joints in the subfloor per ANSI A108 installation standards. One also needs to consider exposure to excessive moisture, direct sunlight and temperature swings based on the final use and application. Both vertical and horizontal applications can be affected by all of these factors, which in turn can cause movement and tension in the finished tile assembly.
There is a general misconception that because ANSI A108 sets its minimum recommended joint width limit to 1/16” – and grout manufacturers produce grouts that can be applied as narrow as 1/16” – that the minimum suitable joint width can also be set to 1/16” for all application types. In some applications, like a kitchen backsplash, a narrow joint may be attainable. However, selecting an arbitrary floor grout joint width as narrow as 1/16” for purely aesthetic reasons, or perceived maintenance, can be extremely problematic not just in terms of the tile assembly’s structure, but also may not be attainable across large areas while keeping adjacent rows aligned. There have been great advancements in manufacturing technologies of both cementitious and non-cementitious grouts as well as grout additives over the years, allowing highly stain-resistant properties to prevent, and in some cases eliminate, the age-old struggle with keeping grout joints clean.
Manufacturers sort tiles by caliber. Tiles of the same size are closer in caliber.
It is not only important to understand the intent of industry and manufacturers’ recommendations prior to joint width specification, but also understand the function and necessity of grout in a tile application as a whole prior to selecting a joint width. The role of grout is not only to bond adjacent tiles to one another, but also absorb and disperse some of the tension caused by the expansion and contraction of tiles and substrates. Although grout should not be used as a standalone waterproofing measure, it does display repellent properties, that when compromised in a wet application, can lead to other failures. In other words, if the joint width is not filled properly, maintained properly, or of sufficient width, then failures may be inevitable. As such, butt-jointing techniques should never be used.
ANSI industry standards for tile are written in such a way to account for both manufacturing and installation tolerances to mitigate potential failures and set expectations of what the end result may look like. When going against industry standards and/or manufacturers’ recommendations, failures may include excessive appearance of lippage, cracking, warping, bond failures, water damage and tenting from tension. Provided that the manufacturer and/or distributor that the tiles were purchased from follow ANSI, ISO or other industry standards for manufacturing, then it can be presumed that the tiles supplied will have certain flatness and dimensional tolerances within a particular range. Since these standards allow for facial dimension variations, the joint width needs to properly account for these variances so that grout joint centerlines can remain straight throughout the application and adjacent tile modules don’t touch at any point. The joint width itself may narrow and widen throughout the application to account for facial variations and floor flatness. ANSI A108.02 Section 4.3.8 addresses this by stating the joint width shall be three times the actual variation of the facial dimensions of the tile supplied.
A larger grout joint is needed for tiles that do not meet the rectified requirements, especially in an offset pattern.
One critical point that is often missed in ANSI A108.02 188.8.131.52 is the additional verbiage that recommends widening the joint of necessity past the standard recommendation to accommodate the specific tile being installed. Without having to measure each tile, it is always best to account for the maximum allowable tolerances whenever possible during specification, which would be approximately 3/16” for pressed porcelain and ceramic tiles and approximately 1/8” for rectified products. This is just a general guide. In some instances the variations in tile dimensions will be minimal, while in other cases they may be riding the maximum tolerance limits or beyond. For example, glazed red-body ceramics are typically developed as a budget-friendly product and may require up to 1/4” joint width depending on the manufacturer’s recommendations instead of the standard recommendation of 3/16” for pressed ceramics due to their inherent size irregularities. With the rise in popularity of long porcelain planks, even though the edges of such tiles may be rectified and the tiles may not have any wedging, the widening of the grout joint width may be necessary to address any inherent warpage that those products tend to display along an edge or diagonal due to their elongated shapes. As such, it may actually be best to install some rectified plank products with a 3/16” joint instead of the generic industry recommendation of 1/8” to help hide any inherent lippage. In other words, due to nuances of manufacturing of certain product types, the manufacturer’s recommendations always prevail over a generic industry guideline to achieve the best end result.
The final layer that provides guidance in proper grout joint width specification is the advancements and availability of leveling clip systems on the market today that help mitigate against the possible negative effects of tile and substrate flatness. Not only is a clip system used as a spacer, but the wedges’ function is to pull tiles from below and simultaneously push tiles down from the top to create a flatter plane in the finished tile install. When potential lippage and floor flatness are being addressed in this manner, a tighter joint may be achieved provided no other jobsite conditions, as previously mentioned, will negatively affect the floor. When opting to go against industry standards or manufacturer recommendations, especially when using a leveling clip system, the specifier and end user must have an understanding, not only of the inherent nature of certain tile product types, but installation tolerances as well. Leveling clip systems are not a final end-all solution to problems related to inherent warpage and joint width spacing, but they do provide an effective measure to mitigate against the negative effects of lippage and challenges in floor flatness.
Narrow joints are possible, but only when the tile is well within the sizing and warpage tolerances for rectified tile. Even so, an offset pattern was not selected because a straight lay masks tile warpage (minimizes lippage) whereas an off-set pattern would have highlighted the tile’s warpage by causing greater inherent/unavoidable lippage in the installation, which would be particularly visible when natural light shines in on the installation. Also, the grout closely matches the tile, making the joints seem smaller/less obvious. Even with all of these factors, the grout joints are 1/8” wide, not 1/16”.
“Self-leveling underlayment” is a bit of a misnomer because it requires the intervention of a thoughtful installer to ensure the best results. Follow these guidelines to prevent issues in your self-leveling underlayment installation.
1. Select a product appropriate for the installation: Know your installation environment and familiarize yourself with the relevant ASTM standards for strength. A commercial floor subject to heavy rolling loads will require a higher-grade self-leveling underlayment than a floor in a single-family home.
Also, it is critical to understand your project timeline and choose a product that fits within the appropriate schedule. Some products may require 24-48 hours prior to installing tile, while other more premium products are ready to accept flooring in as little as 2-4 hours. Consult product data sheets for information on tensile strength, compressive strength and flexural strength, as well as recommended cure times.
2. Stabilize your substrate: Most products require that all surfaces are fully stable and structurally sound prior to the application of a self-leveling underlayment. For example, wood must be securely fastened with screw-type or ring-shank nails and adhesive because if it shifts, it could cause cracking.
3. Prepare your substrate: Make sure to plug all floor openings, gaps and cracks and install termination dams to prevent any seepage. Consult with product manufacturers to determine moisture limitations of the self-leveler, adhesive and flooring to determine if moisture mitigation is needed.
If moisture mitigation is required, this must be done prior to installation of the self-leveling underlayment.
TEC® Level Set® 200 was designed for the fast leveling of floors. It is both pourable and pumpable to fit your job needs.
Self-leveling underlayments (SLUs) require the use of a primer prior to installation. Primer retains the moisture within the self-leveling underlayment to properly cure. Secondarily, it acts as a bonding agent to ensure the SLU bonds properly to the substrate. Refer to the primer label for information regarding application methods and dilution per ASTM F3191.
Beyond priming, most self-leveling underlayments require that the substrate be free from any contaminants that may inhibit bond, including oil, grease, dust, loose or peeling paint, sealers, floor finishes, curing compounds or contaminants. Some underlayments will require a certain concrete surface profile (CSP), and in these cases, mechanical abrasion, like shot-blasting, is required. Make sure the substrate is contaminant free and has the necessary surface profile before starting the pour.
4. Mix properly: Mix your self-leveling underlayment within the water range specified on the bag. Overwatering will lower the strength of the underlayment and can cause cracking and pinholing. Additionally, a white film (efflorescence) may form on the surface of the cured underlayment if the product is overwatered. This film can act as a bond breaker if the mortar bonds to the salts instead of the SLU. Do not over mix it, as this can make it harder to work with and lead to cracking or improper flow. Mix a maximum of two bags at a time when barrel mixing to ensure a proper blend. Follow equipment and product manufacturer’s recommendations when pumping self-leveler.
TEC® Level Set® 200 is walkable in 3-4 hours, making it a great choice for fast turnaround jobs.
5. Be aware of product and environment temperature: Make sure that the temperature of the room is within the manufacturer’s acceptable range. A climate that is too cold or too hot can cause issues, such as increased set time in cool temperatures or reduction in heal time in hot environments. Temperature and humidity will affect flow, working time and set time.
Additionally, the temperature of the powder and the water is crucial. Leaving product in the sun, or in a hot environment may lead to flash setting. In situations where warm product is unavoidable, mixing with cool water may help combat installation issues.
Whether the environment is warm or cool, acclimating the product prior to mixing is a best practice.
TEC® Level Set® 200 delivers extended 25-35 minute working time without compromising flooring installation time.
6. Use as recommended: Manu-facturers will specify the maximum thickness of their product. Some products allow for addition of aggregate to increase the depth of the pour, while others only allow their product to be used neat. Be sure to use the appropriate aggregate size and amount when extending a self-leveling underlayment. If a surface is extremely uneven in an isolated area, a patch may be necessary, rather than a self-leveling underlayment. Consult with manufacturers to determine the most suitable product for your application.
Protect from excessive drying due to air movement. Use of fans or other direct air flow is not recommended, as the surface can be prematurely dried, leading to a weak underlayment.
7. Protect your underlayment: Generally, underlayments are not final wear surfaces. They should be protected from construction trade traffic until final floor covering is applied. Traffic without protection can lead to cracking and disbonding. Do not allow heavy or sharp metal objects to be dragged directly across the surface.
A common theme connects these recommendations: noting and adhering to the manufacturer’s instructions. You must read labels and product data sheets carefully to ensure products perform as desired. If you do have questions, you can always reach out to the product manufacturer.
Those familiar with tile recognize that stunning tile installations have stood the test of time and endured as practical works of art for generations and generations.
Today’s tile setters participate in that tradition of precision and artistry with every job. And there are some techniques that take tile craftsmanship to the next level. Scribing is one such technique.
“Scribing is an art form,” said NTCA member Joshua Nordstrom, of Tierra Tile in Homer, Alaska. “It highlights the level of skill, detail, and abilities that you’re capable of.”
Scribing “gives an install a more artistic feel – it’s more personal – which is great for our industry because as tile setters, we are artists, and it’s nice to be able to do something creative to showcase that fact,” agreed Jason McDaniel, NTCA member of Stoneman Construction, LLC, in Tualatin, Ore.
Scribing is done “when a factory tile meets an organic shape such as pebbles, natural stone, or around an irregular shape,” Nordstrom explained. “Pebble scribing is very common because cutting pebbles in a straight line doesn’t look or feel like a natural transition,” McDaniel added. “Over the past few years, it has become more common to see a pebble scribe.
“Personally, because I like to scribe, I decided to do a mosaic hex scribe and see how that would look,” McDaniel continued. “It looked amazing and now we scribe everything.”
While there are many ways to customize a project, scribing can make the job truly original. Nordstrom says in his Alaskan community, his clients like to incorporate nature endemic to the area into their tile designs, often in bathrooms and entryways. “I offer my clients a personal touch for their tile install, from an elaborate mural to a simple medallion, he said. “I find that I can sell a scribed mosaic in about six out of 10 jobs. Most people like to add just that little touch to set their home apart from the rest.”
Scribing takes a combination of skills, all of which begin with PATIENCE. “Scribing is a game of patience that requires time and experience to master,” Nordstrom pointed out. “It takes as long as it takes,” said Kyle Gaudet of Flawless Floorz, a NTCA member in Brentwood, N.H., “Take your time – even extra time – until you’re comfortable with what you’re doing.”
The essential skill of templating
Nordstrom’s Kraken traced life size on a Tyvek ‘canvas.’
An essential skill to clean scribing is templating. “I template everything when it comes to scribing a mosaic,” Nordstrom said. “It all starts with a scaled drawing that gets blown up with a overhead projector and traced life size on a Tyvek ‘canvas.’ Once it’s all colored and labeled, I go over it with tracing paper creating each individual template. Once everything is cut and installed on a fiberglass mesh, I lay the mosaic over the field tile, trace it out and scribe it in.”
McDaniel’s first step is templating as well. “I precut all of my tiles for the floor or wall and then I overlay the pebbles or mosaic that I am going to scribe,” he explained. “I trace the outside of the tile with a sharpie and then use a grinder and remove the sharpie mark. Once the scribe is completed I take a diamond pad or sanding disc to ease over the cuts and make them look smooth and finished, taking all of the chips out of the scribed area. I have found that precutting the area and overlaying is by far the easiest method to use when scribing.”
McDaniel’s pebble scribing
McDaniel didn’t always use this method. “The first scribe I ever did was a pebble scribe,” he said. “I made templates using wax paper, which was grueling and time consuming, and not as accurate as overlaying and tracing. Overlaying and tracing allows you to set the field tile first, letting that area dry. Coming back in the next day and setting your scribe mosaic allows you to make the transition between field tile and mosaic tile perfectly flush, as it should be.”
Gaudet uses a “traditional” 2” piece of the tile for a scribing piece, marking every piece contour by contour. “I also use a 5” and 4” angle grinder, nippers and dry polishing pads,” he said.
Scribing tools; dealing with varying thicknesses
In terms of tools, McDaniel scribes everything with a grinder with a 6” turbo mesh blade, which gives him the best accuracy given the amount of plunge cutting necessary in scribing. “The larger blade allows you to go deeper into the tile before you hit your grinder. Saw horses and clamps are a must have to hold the pieces in place. After I finish my scribe, I ease all of my edges with a 100 grit sanding disc, or a Dremel tool for tighter corners. I am aware that Joshua Nordstrom does all of his scribing with a tile saw and I find that to be absolutely amazing!”
After everything is cut and installed on a fiberglass mesh, Nordstrom lays the mosaic over the field tile, traces it out and scribes it in.
In fact, Nordstrom uses a 10” wet saw, resorting to a grinder only if it’s necessary to remove some material from the tile back to achieve the same thickness between different tiles. “I have learned over the years that installing a fiberglass mesh on the backs of my mosaics really simplifies the installation,” he said.
McDaniel said scribes can be mounted on membranes or thin backer board, though he prefers to “screed my scribed area with thinset so that I can adjust each piece meticulously, insuring that I have a consistent grout line that matches the rest of my install. It also depends on what you are scribing. Sometimes glass mosaics can be difficult to deal with, so pre-mounting them is a worthwhile step.”
Considering thickness is key when scribing, and matching the tiles or grinding the tile backs is sometimes necessary to achieve the proper thickness. “Sometimes when installing you may need to use different trowel sizes to accommodate the height difference in the tile,” Nordstrom said.
McDaniel said his greatest scribing challenge was installing pebble mosaics around a large piece of walnut in an entryway.
McDaniel tells about his most challenging scribing task – installing pebble mosaics around a large piece of walnut in an entryway. Engineering expansion and elevations among the four surfaces and four thicknesses was tricky, he said. “With anything tile, planning ahead and having a game plan going in is essential to being successful,” he said. “Having a start and stop point, keeping your area clean, making sure you have expansion, using anti-fracture membranes, uncoupling membranes, better setting materials, non-sag thinsets; all of these things make your job easier.”
Pricing the job is personal. Nordstrom figures out how many hours it will take him to cut and install, price it on an hourly or date rate, and figure in a little extra for margin of error. Gaudet, whose company is new to scribing, said his client was initially resistant to scribing and the associated upcharge. But “after showing him a few of the pieces, he was in total agreement with my opinion to scribe that wall,” and to agree to pay the upcharge due to the look.
McDaniel, though, doesn’t charge extra for scribing. “I have never made money on a scribe,” he said. “I do it because I want my work to stand out. I want to be known as an artist and a craftsman. Maybe someday I will make money from my scribing ability, but for now I am okay with being considered a ‘Tile Badass’.”
In addition to taking your time, starting small and having patience, McDaniel said the most important thing when scribing is to have confidence. “Know that you can do it; know that you are doing something different that is going to stand out when seen.” He also recommended following the work of several tile setters who have been successful with scribing – and reaching out to them for advice: Robert Davis, Mike Soho, Zack Bonfilio, Tom Habelt, Carl Leonard, and Hawthorne Tile. In addition, he recommended viewing the videos and pictures posted in several tile-centric Facebook groups: Global Tile Posse, Tile Geeks, Tile Love 2.0, The Misfit Tilers, and Tilers Talk to get more information and inspiration.
If you are looking to give it a try, here is the first video in a series Nordstrom created on scribing. The remaining videos are available on the NTCA YouTube channel.
The Occupational Safety and Health Administration (OSHA) has announced plans to reopen the Occupational Exposure to Respirable Crystalline Silica ruling, primarily focused on possible changes to Table 1 of the silica standard. Table 1 is a listing of construction tasks with engineering controls, work practices, and possible respiratory protection that provides compliance certainty for those tasks. Currently it’s comprised of only 18 common construction operations, each with their own limitations. The list can be found at https://www.osha.gov/silica/Table1sect1926.1153.pdf or https://bit.ly/2ZaS0zg.
The notice to reopen the rule is currently at the Office of Management and Budget (OMB) for review before publication in the Federal Register. A 60- to 90-day comment period is expected once the notice is published. To take advantage of this unique opportunity, companies wanting changes to Table 1 must organize quickly and assemble data to support their requests.
If a task is listed on Table 1, and the employer ensures that all requirements are followed, the employer does not have to conduct an exposure assessment for that operation. However, the list is far from exhaustive and includes limitations. For example:
Several tasks, including cutting fiber-cement backer boards, are limited to only being conducted outdoors. This excludes not only performing the task indoors, but also in “enclosed areas,” which would include garages and many other partially enclosed locations.
Many tasks include only one type of engineering control, often water-based. In some instances, vacuum-based controls are currently available but have not been included in Table 1.
Some tasks limit the size of the blades that can be used.
In addition, there are some common activities that are not included in Table 1, such as:
Mixing mortar, self-leveling underlayment (SLU), and other silica-containing materials using a variety of powered equipment.
Shot blasting for floor preparation.
Excerpt from Table 1 showing exposure control methods required for stationary masonry saws.
Opportunity for changesto table 1
After the initial announcement to reopen the Occupational Exposure to Respirable Crystalline Silica ruling in late 2018, Tile Council of North America (TCNA) staff met with OSHA to discuss the details of this upcoming action. TCNA’s understanding is that OSHA will be looking for at least two types of changes to Table 1:
New additions. Submittals can include proposed categories, engineering controls, and PPE requirements (for example, if supported by data, mortar mixing with a 300-rpm drill equipped with a mixing blade, adding water before powder, and without PPE if under four hours per day).
Enhanced equipment requirements. Industry can propose new engineering control requirements for tasks already on Table 1, which could change the PPE requirements. For example:
With air filtration or water flow rates set above the current thresholds, perhaps PPE requirements could be less restrictive.
Some tasks are currently limited to outdoor use only. With data from indoor operations, it may be possible to show that operations conducted indoors, or in enclosed areas, are also below the action level of the rule for certain tasks.
Scoring and snapping is not currently listed in Table 1, however in their FAQs, OSHA lists the use of score and snap cutters (or tile splitters, as they refer to them) as one of the activities not expected to expose workers to silica levels of concern.
Beyond adding tasks to Table 1, companies can also use this opportunity to clarify issues they identified through efforts to implement the rule. For example, some companies have raised the question of how to differentiate between a grinder and a saw, especially when the same piece of equipment can be used in both capacities. Grinders and saws are currently treated differently on Table 1. While presumably the difference lies in whether a saw blade or grinding wheel is attached, with Table 1 being revised, that can be clarified by OSHA with no ambiguity for the OSHA inspector and installation company.
Mixing mortar is not one of the 18 construction tasks listed on Table 1. Companies that desire changes to Table 1 should prepare now by formulating their request and evaluating their data.
The process to potentially change Table 1 will be lengthy, with revised standards likely not out for at least a year. However,data provided to OSHA for changes to Table 1 may be immediately useful as “credible data” when assessing exposure to employees, which is required by the standard for all tasks not following Table 1 requirements.
The window to revise Table 1 is relatively narrow. Given OSHA’s schedule, we expect the notice requesting data to be published this summer, with the 60- to 90-day comment period extending into early fall. Companies that desire changes to Table 1 should prepare now by formulating their request and evaluating their data. If additional data is needed to fully characterize exposure, the effect of controls, or required PPE, companies need to identify that right away to collect the required information.
This article is to help raise awareness of what TCNA staff believe are important issues for the reader. Please understand, however, that these issues often involve complex regulatory issues that are not easily summarized and that may vary in application based on specific facts and circumstances. Therefore, this article is offered as is, for informational purposes only, and readers should not rely on it for legal or other professional advice. Readers should conduct their own review and seek appropriate professional advice for their specific
In 1987, a new product category was launched in the North American Tile industry called “Uncoupling Membrane.” The product – an orange membrane – was made of polyethylene, ribbed in one direction and had a polypropylene mesh heat-bonded on the underside. This product was only 3/16” (4.5 mm) thick and 3’ 3” (1 m) wide and only weighed 45 lbs. (20.4kg) for a 323 sq. ft. (30 sq.m.) roll.
Surprisingly, one of the most popular uses of this very flexible and non-rigid membrane was over plywood substrates, including over a single layer of plywood. In 1999, the first detail for a “Proprietary Membrane” with double layer of wood subfloor on 24” (600 mm) on-center (o.c.) joist spacing was introduced to the TCNA Handbook (F147). Then, only two years later in 2001, a second detail was added to the Handbook for going over a single-layer plywood floor on 19.2” (480 mm) o.c. joists with an “uncoupling system.” There was no reference to the manufacturer under limitations. The term “uncoupling” was substituted for “proprietary membrane,” and a definition was added to the prologue:
“Uncoupling Systems: A system that separates the finished surface from the substrate to allow the independent movement between the two and prevent the transfer of stresses to the tiled surfaces.”
For those of you who attended that meeting in Clemson, S.C., you will remember that this was the year that the TCNAHandbook Committee voted to approve removal of anything in the Handbook that had proprietary names, which included the section for “Floors Sound Rated.” Then around 2006-2007, a directive was issued to describe a “DITRA”-like product. This definition resulted:
“Uncoupling membrane: A plastic membrane system geometrically configured to provide air space between the tile and the substrate to allow independent movement between the two and limit the transfer of the stresses.”
The last detail added to the TCNAHandbook for uncoupling was in 2007 for “Young Concrete” Detail F128. The concern with young/green concrete is that the concrete slab has large amounts of residual moisture that still need to be released from the concrete. This release of moisture can affect the curing of the mortar and the grout. Many crack-isolation/waterproofing membranes – specifically those membranes that are flat – have limited resistance to pressure from moisture since there is nowhere for the moisture to be released. This in turn creates pressure that can cause the membrane to bubble or debond from the concrete slab. The TCNA Handbook declares that an uncoupling membrane must have free space or empty cavities on the underside of the membrane that inherently allow for moisture/vapor release and eventually equalization.
The TCNA Handbook prologue uncoupling definition was updated again in 2014 to include:
“The uncoupling membrane must achieve 50 PSI or greater shear bond strength in 7 days per the test method in ANSI A118.12 Section 5.1.3.”
This addition was in response to the concerns conveyed by labor and some forensic consultants that there were certain so-called “uncoupling membranes” that were failing to the extent of several millions of dollars for repair and damages. The main mode of failure was traced to the bond between the substrate (majority plywood) and the underside of the membrane where the fleece/mesh or other had delaminated. Until an ANSI standard is created for uncoupling, this requirement is a reasonable stop-gap to identify those membranes that are not performing.
The look of uncoupling has changed over the years but the basic criterion has remained the same: a configured membrane with open-air space to allow for independent movement between the tile and the substrate. Some of the newest additions to the uncoupling category now incorporate a floor warming system and have an optional integrated sound control and thermal break (for quicker heating reaction time).
The need for a standard
Shear testing an uncoupling membrane in the lab using the Instron machine.
The need for an ANSI standard has become more essential in North America than ever before, with the proliferation of new uncoupling membranes that have emerged in the market recently. The good news is that the Materials and Methods Standards Association (MMSA) has had a subcommittee that has been working on developing a standard now for several years. In fact, a draft standard has been prepared and will be presented at the next Total Solutions Plus (TSP) conference this year being held in Nashville, Tenn., October 26 – 29. Those companies, organizations and associations involved in this effort include: ARDEX Americas, Custom Building Products; ISOLA; LATICRETE; MAPEI; NAC Products; The Noble Company; Schluter Systems, LLC; and TCNA. Most of the details in the TCNA Handbook that were identified earlier will be part of the testing criteria. In addition, “Point Loading” and “Fungus/Microorganism Resistance” will be included. Two additional testing criteria under development are vapor transmission and shears to evaluate the stress/strain relationship between uncoupling membranes and other membranes that are flat. This testing has been an international effort that has displayed some promising results.
Uncoupling membrane in a commercial building.
In addition to the MMSA subcommittee working on an uncoupling standard, the International Organization for Standardization (ISO) has established WG 11 “Uncoupling Membranes for Ceramic Tile Installation” under the auspices of TC-189 (Technical Committee for Ceramic Tile). Some of the same participants are in both committees, so there has been very good communication and collaboration to ultimately achieve the best standards for both organizations. Other areas that are being pursued by the ISO group are “tensile” and “compression” testing.
In summary, uncoupling membranes have come a long way since the introduction of the very first membrane in 1987. Use of these membranes has proliferated over a huge array of substrates and conditions, allowing the tile industry to complete successful installations over some of the most challenging applications. The performance standards for uncoupling have been a long time coming, but creating a suitable standard for a product that works more off of physics than chemistry is not an easy or simple task.
Uncoupling membrane in a commercial building with large format tile.
Does lack of willingness to purchase installation excellence exclude tile setters who craft quality work?
Coverings is not only an opportunity to see firsthand the latest tile and stone styles and trends; it’s an opportunity to learn about the latest technical and installation challenges and the efforts underway to address them. One such discussion at this year’s show last month was the premise that an increasing number of installers are not using measurements and chalk lines to square up and lay out their tile installations. Instead, they are relying on hard spacers, usually made of plastic, to determine the grout joint width and tile positioning, which can result in misaligned tiles.
Contrasting grout and tile make misalignment more obvious than less-contrasting grout and tile.
NTCA requested this topic be included on the agenda for the ANSI ASC A108 Committee meeting held at the show. The discussion was initiated by NTCA Board member and Technical Committee Chairperson James Woelfel, who is active in development of installer and contractor best practices through involvement in and leadership of numerous technical committees. Reliance on spacers has become a critical issue, according to Woelfel, who, in addition to contracting, is engaged in inspection and consulting. He says this problem is the cause of about 80% of the inspections he has performed so far in 2019.
The committee discussed the well-understood and accepted function of the grout joint as the necessary adjustable component of every tile installation that accommodates variations in tile sizing, an inherent characteristic of tile. But hard spacers inhibit that adjustability factor. Accordingly, the less consistently-sized a tile is, the greater the misalignment that will be caused by hard spacers because of the greater need to adjust the grout joint for the tile size differences.
Rectified tile has less size variation, stipulated by ANSI A137.1, compared to calibrated tile, for which more size variation is allowed.
Conversely, the problem that Woelfel believes is on the rise would be less pronounced with rectified tile. This is because of the very small amount of size variation allowed for rectified tile, per ANSI A137.1, as compared to tile classified as calibrated tile, which is allowed more variation.
Tile classified as “natural” has very intentional size variation for aesthetic purposes and is allowed the greatest amount, and many tiles have even greater intentional variation and fall outside the tile standard completely.
But spacers themselves aren’t the enemy. They can be combined, or adjustable varieties can be used, to produce a good end result even when there is significant size variation in the tile.
Exploring the cause of the issue
The root cause of the issue is debatable. Perhaps there is a lack of awareness of size variation and how to deal with it, and a lack of qualified installers despite the availability of information and instruction available, especially online. Or, perhaps installers know better, but are working at rates that unquestionably require speed over precision. Is there a lack of willingness by homeowners and GCs to “purchase” installation excellence that excludes those who would take the time and make the effort to make aesthetic adjustments?
Spacers used in combination to give tile with purposeful size variation a consistent overall appearance.
One can only speculate. Most inspection reports address only whether an installation does or does not meet industry standards. When it does not, the common presumption is that installer error is wholly to blame. But a deeper-diving, less black-and-white assessment might reveal significant culpability of homeowners and GCs choosing not to hire qualified labor.
It’s an important question for the industry. Perhaps Woelfel’s spacer-related observations are a microcosm. Does an increase in improper spacer use signal worsening undervaluation of craftworkers and trade work? We should try to find out.
Some installers use compressible materials like rope to space tile.
If misaligned tile due to spacer use reflects a shrinking willingness to purchase trade excellence, could we trace the lack of qualified labor back to that lack of demand? Could it be considered a labor market correction, i.e., a generalized lowering of output quality that equalizes the supply side with the demand side?
It may sound controversial but does the opposing theory make sense? Is it possible that the tile-consuming public not only wants – but is generally willing to purchase excellence – yet contractors and installers are either disinclined or unable to find a way to meet that demand despite the profitability of doing so? If that were true, contractors that do deliver quality work would have an almost unmanageable backlog of work, while subpar contractors would get very little work and be virtually driven out. Unfortunately, it seems the opposite is the case: quality contractors often struggle to get work, and report that the projects they bid on are routinely awarded to contractors that do not provide the same level of installation quality.
Determining precise layouts
Whatever the reason for it, the implications aren’t limited to some misaligned tiles. Even if all the tiles on a job were miraculously the exact same size, with zero adjustability needed, Woelfel’s observations still signal a problem.
The method of using measurements and chalk lines to lay out an installation is the skill that enables the tile installation to be oriented in the best way possible for a given tile and pattern in a given space. Laying out tile is the process of determining the size and placement of cuts (partial tiles) before any tile is set. Especially for larger installations, it’s a decision-making process, which may even involve a home or building owner since the “best layout” is often subjective.
One homeowner might want full tile at a certain threshold or transition to other flooring, regardless of how that arrangement decision impacts the tiles on the opposite side of the room; while another individual would prefer a more centered design.
Tiling the main aisles of a furniture showroom requires precise layout to ensure tile rows are aligned on center with columns.
Only through professional layout processes can the layout options, including the aesthetic pros and cons of each option, be known and evaluated and an informed decision be made. Similarly, the professional layout process enables installers to adjust a layout to meet specific points and locations as needed in-situ. Installers may have to ever-so-slightly expand or compress a layout in order to “make it work,” imperceptibly, and over the course of multiple rows.
Several ANSI Committee members said they support Woelfel’s thinking that language could be added to ANSI standards and/or the TCNA Handbook relating to the potential for spacers to result in misaligned tiles. As part of the related awareness efforts, the larger implications should be emphasized. The idea is to not only avoid crooked tiles due to spacers, but to ensure that the highest level of craftsmanship is available wherever and whenever needed. This is not accomplished by seeking out qualified installers and companies only for the most critical projects, but rather by helping to sustain them by being their regular partner on the jobs in between.
CTIOA field report provides guidelines and best practices to complement industry standards
Industry standards cover the basics of common tile applications, like pools, but contractors who take them on will tell you there’s a lot more to know. That’s not a criticism; it’s just the reality of what can reasonably be expected. An addition or revision to the TCNA Handbook or the ANSI standards often takes several years of behind-the-scenes research, information sharing, and collaboration before it’s proposed. Once it is, the consensus process sometimes dilutes the language or intent, or limits the scope of a proposal.
TCNA Handbook method P602 is for installation of a mortar bed and tile in a concrete, shotcrete, or CMU pool tank waterproofed with cementitious waterproofing, the performance of which can be enhanced by application of a penetrating colloidal silicate beforehand.
Think about asking your extended family to agree on where to go on vacation together this summer and it’s easy to understand the challenge of getting 50 voters from various segments of the tile industry on the same page. While approved language is solid because of the rigor of the process, there’s often a larger body of information – a mix of facts, opinions, experiences, and preferences – that could also inform contractors’ decisions and processes.
For pools, spas, and similar submerged installations, a plethora of additional such information was compiled by a Ceramic Tile Institute of America (CTIOA) pool-focused technical group, to provide non-proprietary options and best practices when the substrate is cast-in-place concrete, gunite, Shotcrete, or cinder block. The 17-page report includes sections on evaluating the structure/shell, maintenance, pool water chemistry, and more.
Especially interesting and relevant to tile contractors is the section on the tile/coping interface, which is categorized in the report under five general design options on pages 2-5, printed here verbatim:
Cantilevered concrete decking, image courtesy of CTIOA.
Cantilevered concrete decking:
A concrete deck around the pool spanning over the bond beam and waterline tile in a manner allowing the deck to “slip” back and forth as needed. This is usually accomplished with a trowelable membrane, #15 felt paper, 6mil. plastic or equal. A movement joint is then placed between the coping and the top of the pool tile.
Cast in place concrete coping: Concrete coping formed on top of a bond beam, extending over the edge of a pool by 2” to 3” and generally terminates in line with the back of the bond beam. Any concrete sub-base or decking that butts up to the coping and/or pool shell must have an expansion provision between the two.
Pre-Cast Coping, image courtesy of CTIOA.
Pre-Cast Coping: This coping is generally cast into molds off-site using concrete or pressed clay, allowed to cure and then brought to the site for installation. It’s made in straight pieces, end caps, and varying radiuses that will accommodate different pool shapes.
Quarried Stone Coping: Stone of various species, sizes, shapes and thickness installed onto the top of the bond beam.
Mechanically Fastened Coping: Commonly used in Rim Flow and Slot drain pools, this type of coping is generally attached by fasteners to structural systems spanning over a trough designed for water to flow into. The coping is flush with the decking and the top of the tile, allowing a slot of 1/4” to 1/2” in width for water flow.
Mechanically Fastened Coping, image courtesy of CTIOA.
The report notes that “the interface of coping and tile as they relate to the bond beam of pools and adjoining decking behind them can account for a significant percentage of pool tile failures when installed improperly… often a result of pressure applied to the pool shell, coping, and /or tile, from pool decking, and adjoining structures.” To avoid tile/coping interface related problems, the report provides “key points to keep in mind when installing coping:”
To avoid putting pressure on waterline tile, cantilevered decking “must be free to slide over the top of pool bond beams” or “must be raised and bonded mechanically or chemically to the existing bond beam, bringing it up to the same plane as the top of the waterline tile.”
Movement joints should be installed between the tile and the coping.
Place cast-in-place coping “over a bond beam that is on the same plane as the top of the waterline tile,” bond it to the bond beam (unless intended as floating/unbonded), terminate the coping (its back side) where the pool structure terminates, and provide movement accommodation between the back side and any abutting material or structure, such as decking.
Ensure a “positive bond” between pre-cast coping (including quarried stone) and the bond beam, which can be accomplished by a thin-set or mud-set method, both of which are described in the report.
In addition to the pool/coping interface information, contractors will also find useful details to consider on surface preparation, mortar bed scratch coating and floating, tile installation, and necessary cure time. While much of the report relates to design, decisions, and work that falls outside a tile contractor’s typical scope of work and responsibility, it’s information that can shed light on potential causes of tile issues, should they occur, for example faulty pool start up or maintenance practices that can adversely affect a correctly done tile installation. The combined “how to” and troubleshooting make the CTIOA report on tiling pools an essential reference for contractors that work on pools, in addition to ANSI standards and TCNA Handbook methods.
The report is available via the site at CTIOA.org.
This article focuses on design concepts that should be incorporated into plans and specifications for curbless showers in new construction. Other challenges and options come into play for curbless showers when these design requirements have not been included (e.g., remodel projects) and the additional requirements are for a curbless shower to also be “accessible,” or ADA compliant.
A few factors are fueling growing popularity in the United States of curbless showers, also commonly referred to as “zero entry” showers. An aging population is a main one. Whether an older individual is “aging-in-place” or has opted to relocate to a community or facility, a curbless shower is often more desirable and sometimes even necessary to help people cope with physical changes that they may begin to experience that can make showering difficult or even dangerous. At the same time, thanks to a proliferation of fashion-forward products and systems that facilitate elimination of the shower curb, people of all ages are “going curbless” purely for the sophisticated, streamlined design.
Regardless of the reasons for it, the noticeable shift toward curbless showers is making it increasingly important for building design professionals and tile contractors to know the unique and critical shower design and installation requirements when there will be no curb at the shower entry to function as a dam. Proper planning and high-tech installation materials and shower components are key to containing the water and channeling to a drain, all of which can be applied to the even more challenging goal for the entry into the bathroom to also be transition-free.
Recessing the subfloor
A shower cannot be totally curbless unless the subfloor where the shower will be constructed is recessed, and the recess is sufficient to accommodate the combined thickness of all the materials below the tile. The size of the shower and placement of the drain(s) are key factors in determining the required recess, as they’ll dictate the required thickness of the floor mud, foam shower base, or other material used to form the sloped base for the tiled shower floor.
Diagram of a shower base constructed of a topically-waterproofed mortar bed (bonded to concrete) and a bonding-flange drain, recessed to facilitate a curbless shower entry
The installation method or system that will be used is also key, as they vary in thickness. Some are thinner by design specifically to make it easier to construct a curbless shower. The use of an ANSI A118.10-compliant, thin, load-bearing waterproofing membrane directly below the shower floor tile – instead of a traditional shower pan membrane underneath a mortar bed – results in a lower profile system without sacrificing functionality. Bonding flange drains and linear drains also offer reduced thickness of the shower base, in many cases requiring no more than 3/4” (mortar bed or preformed pan) at the thickest point, whereas a traditional clamping ring style drain, such as those shown in many TCNA Handbook methods, (e.g. Method B415) requires a 1-1/4” to 2” mortar bed.
A single sloping plane is possible with a linear drain, which gives a streamlined appearance and allows large tiles to be used; just be sure the tile layout on the walls will facilitate the non-level floor perimeter.
Thus, for the tile contractor to be able to deliver a curbless shower, the specifics of how the shower will be constructed must be determined at the outset so their dimensions can be incorporated into the building’s rough-in plans. This is much earlier than is often the case, which highlights the importance of advance planning when it comes to curbless showers.
Another piece of the puzzle is drain location. In many cases linear drains and bonding-flange drains can be located in various places within a shower compartment – at any of the shower walls, at the shower entrance, or mid-floor. Perhaps more important than its impact on the required floor recess, ideal drain location is critical to how the shower water will flow and drain. Effective draining – versus aesthetic preference – should drive the placement decision. In many cases placement away from the shower entry is optimal.
During the design phase, consideration should also be given to defining the shower floor space. In other words, what are the extents of the shower floor? In some cases, in larger showers or open-design showers where the shower floor freely flows into the restroom areas, a secondary drain may be required to collect any water that may flow out of the shower compartment or overrun the main shower drain due to the momentum of the water. Also, showers with multiple heads/jets may require additional drains to handle the water flow.
Slope of the shower floor
The International Plumbing Code (IPC) requires a slope of 1/4” per foot (IPC 417.5.2 Shower Lining) for shower floors, which is echoed in the TCNA Handbook shower receptor methods. Recessing the subfloor or substrate under a shower allows the finished floor to start sloping from the height of the floor outside the shower, rather than building up a shower base to provide slope to drain, as required when there is no recess in which to countersink the shower base, which therefore requires a curb.
Sometimes less slope is specified in a curbless shower, such as 1/8” per foot. In some jurisdictions, a slope of 3/16” per foot or 1/8” per foot could be allowed for a roll-in shower designed to comply with the Americans With Disabilities Act (ADA). However, it is important to note that reducing slope greatly reduces the draining efficiency of the shower. There just isn’t enough slope to properly evacuate the water, which can result in standing water at any given time, a different possible safety concern. In addition to considering these tradeoffs, design professionals should also consult local building and plumbing codes and officials on a regular basis to ensure baseline compliance with the most current requirements, including the latest ADA parameters when ADA compliance is also intended.
Although tile contractors should in theory be able to follow specifications as written, when less than 1/4” per foot slope is specified, it may be worth reconfirming the desired and/or necessary slope with the general contractor and/or project design professional before proceeding. The same could be said for the specified slopes and drains, and the resulting floor recess needed to accommodate them. If a reconfiguration is necessary, a proactive approach might avoid finger pointing and delayed payment later on, or help to build relationships that will lead to more work.
But regardless of how or when potential design issues are addressed – some contractors prefer to wait until they’ve been awarded a job – what’s not optional is a good understanding of the critical design elements for curbless showers. Even when it’s a designer’s responsibility to design a shower that’s curbless and drains effectively, tile contractors will no doubt discover – and therefore have to address – various design and rough-in execution flaws as part of the process.
Building design guidelines and additional measures to accommodate sustained concentrated loads
This article was derived from an article by Dr. Frank Woeste, P.E., Professor Emeritus at Virginia Tech and a wood construction consultant, and Peter Nielsen, cofounder of MGNT Products Group, LLC, a consulting and product design company for the tile and construction industries. This version of the information was generated by NTCA to provide a brief overview of their wood framing recommendations for hard surface flooring.
Two kinds of designers are involved in construction: design professionals responsible for performance and structural integrity and interior-focused designers responsible for the final appearance. Although they have very different roles, some of their decisions should be coordinated. For example, they should join forces when hard surface flooring – like tile and stone – is selected since these materials are on the heavier end of the spectrum, requiring more robust structures to support their weight. Hard surface floors are also more susceptible to problems than flexible floor types are when the weight of a concentrated load, like a dreamy kitchen island, is not adequately designed for. This article provides guidelines to design professionals for specifying adequately supportive structures for tile and stone floors in new construction wood frame buildings.
Designing for dead load
Sagging book shelves illustrate the concept of creep deflection; over time, shelves that are not strong enough for the weight they are loaded up with will bow.
A key factor is “dead load,” which is the cumulative weight of everything that a structure needs to support continually, including the flooring. When the actual dead load in a wood frame structure exceeds what was designed for, it over stresses the wood framing and over time can result in excessive “creep deflection,” a permanent bowing of the structure. An easy way to envision creep deflection is to picture an overloaded bookcase. The shelves will bow over time – and permanently – under the weight of the books.
Similarly, a home or building can be overloaded, for example by being structurally designed for luxury vinyl planks (LVP) flooring rather than the interior designer’s vision for ceramic planks. Some creep deflection is inherent and expected in wood frame construction, and not an issue for tile and stone floors. Overloading is what causes excessive creep deflection, possibly beyond what a tile or stone floor can withstand. Potential for and severity of a tile flooring issue because of excessive creep is tied to the amount of overloading and passage of time.
Weighty design features, like large kitchen islands with solid surface tops, and heavier-than-usual appliances, such as a Sub-Zero refrigerator, are examples of concentrated dead loads that additionally need to be designed for, structurally. This is true regardless of flooring type, but something to be especially aware of when the floor will be ceramic or stone tile. That’s because rigid, hard surface flooring materials are where concentrated overloading of a wood frame structure might become visually apparent, in the form of cracks, due to their inability to bend.
Baseline weights to factor into dead load
To facilitate adequate structural design for tile and stone floors, the TCNA Handbook for Ceramic, Glass and Stone Tile Installation provides the approximate per square foot weight of tile, stone, and installation materials, individually by material type (i.e., 1/2” thick cement board weighs 4 lbs. per square foot) as well as cumulatively by installation method (i.e., Method F144 weighs 8 or 10 lbs. per square foot, depending on whether 1/4” or 1/2” cement board is used). Using this information, located in Appendix B, building designers can arrive at accurate dead loads.
Appendix B of the TCNA Handbook is a compilation of material and system weights.
Method F141 Stone weighs 23 pounds/square foot with a 1-1/4” mortar bed.
Accurate dead load is important because dead load influences the maximum span (length) of wood joist that can be used, per International Residential Code (IRC) guidelines. These guidelines provide maximum allowable joist span separately for an assumed dead load of 10 psf and 20 psf. Remember though, dead load is not just the flooring. So, while the separate span tables may be generally used according to flooring type (e.g., follow guidelines for 10 psf dead load when lighter floorings like carpet will be installed, and guidelines for 20 psf dead load for tile and stone), one should not assume they apply in all situations. Additional dead load could be present from other elements, causing total dead load to exceed 10 psf where a lighter floor finish will be installed or exceeding 20 psf where ceramic or stone tile will be installed. Not to mention, some tile and stone installation methods on their own exceed 20 psf, which demonstrates that IRC span tables aren’t always enough.
Research indicates that an even more important consideration for tile and stone floors in wood frame construction is the thickness/stiffness of the subfloor, although not necessarily because of system-creep-inducing overload. Rather, the subfloor sheathing could simply deflect (bend) between joists under an applied load more than a hard surface tile can withstand, even if the sheathing is otherwise adequate within the full design scheme to support the expected loads.
In Method F144, the wood subfloor can be 19/32” thick or 23/32” thick and relates to whether the installation methods falls under the residential or light commercial service rating.
This industry-specific consideration, not addressed in IRC, is addressed in the TCNA Handbook through more stringent deflection limits. Specifically, the TCNAHandbook limits deflection under concentrated loads, whereas IRC deflection limits are for uniform loads. What this means for building designers is that the minimum subfloor thickness/stiffness required by code for strength may not be enough. A thicker/stiffer subfloor may be needed to limit subfloor bending between joists. More robust framing may also be needed, again to go beyond the strength consideration to further limit bending related to concentrated loads. The heavier and more concentrated the load, the greater the need to beef up the floor framing to limit bending.
An example: the largekitchen island
As an example, consider the large kitchen island scenario. With 30mm (3cm) thick stone tops and normal contents being stored inside, this popular kitchen feature could present a 40 psf dead load, calculated by using the square footage of the island’s footprint as the area. In service, the framing and subflooring directly below and around the island is subjected to a substantial sustained load that produces creep deflection, but only in that area. As such, for hard surface floors, building design should incorporate more stringent framing requirements in areas where concentrated dead loads are expected, with kitchen islands a particular focus because of their widespread use.
Because this kitchen island is oriented parallel with the wood joists, its weight is on fewer framing members.
It’s not practical, though, to expect a customized calculation and specification for every kitchen island. A more practical approach would be to follow general guidelines that are widely effective and easily incorporated into documents and processes.
Since large kitchen islands are frequently paired with ceramic or stone flooring, it makes sense to have the following structural design parameters specifically attached to them:
For solid-sawn and I-joists: joist spacing beneath kitchen islands shall be reduced by one-half and indicated on the joist framing plan.
For floor trusses: floor trusses beneath kitchen islands shall be doubled.
Designing for hard surfaces checklist
These suggestions are in addition to the following recommendations, some of which were provided earlier in the article but are restated here in the interest of supplying a complete “designing for hard surfaces checklist”:
Prepare construction documents that contain:
º the TCNA Handbook installation method
º the weight of the installation method (from TCNA Handbook Appendix B)
º the footprint of the kitchen island (and other heavy equipment)
º a specification that joists shall be doubled, or spacing reduced by half, beneath an island
Require floor system designs based on a “total load” that includes the actual weight of the installation method
Upgrade subfloor thickness (above what is given in the TCNA Handbook method being used)
Require strongback bracing for floor trusses to minimize differential deflection of joists
Offer customers (homebuyers, owners) floor framing and subfloor “upgrades” for added protection against the likelihood of tile and grout cracks and annoying floor vibrations
The generalized “overbuilding” that some of these recommendations suggest may not seem an easy ask in an industry that prizes value engineering. But they do have enormous value – not in material cost savings – but from having effective boilerplate solutions to a common design challenge that are also practical with respect to implementation. Tile and stone professionals would be well served if these guidelines were better known and understood by building designers. TileLetter readers are encouraged to help make that happen by circulating and posting the information freely.